This invention relates to a monitor for temperature and pressure utilizing an interference filter, and is particularly related to monitors for blood pressure and temperature.
Three principal types of blood pressure monitors are known. The conventional sphygmomanometer employs a cuff wrapped around a patient's arm with means to inflate the cuff and to measure the pressure that the patient's blood vessels put upon the cuff. This is entirely unsuitable for continuous real time monitoring of the patient's blood pressure. The systems currently employed for continuous real time measurement of a patient's blood pressure require a catheter to be inserted in the patient's blood vessel. The catheter is filled with a saline solution that continuously drips into the patient's body. A pressure transducer is mounted in the tubing that conveys the saline solution to the catheter. The blood pressure transducer converts the fluid pressure in the catheter to an electrical signal proportional to the patient's blood pressure. See application Serial No. 07/072,909, filed July 14, 1987.
A third type of the blood pressure transducer, found more in the literature than in actual practice, involves the insertion into the patient's blood vessel of a pressure sensor, the sensor being connected by optical fibers to apparatus for converting the output from the sensor to blood pressure units. The sensor generally is some type of mechanical device or diaphragm that flexes with changes of pressure and the amount of flexure is somehow measured using the optical system. See Boiarski, U.S. Pat. No. 4,727,730, issued Mar. 1, 1988.
Of the three systems described above, the first does not produce real time continuous monitoring. The third has not enjoyed any commercial success. The second, while in widespread use, is expensive and somewhat cumbersome, requiring both the supply of saline solution and a system of stopcocks and flush devices as well as the transducer that is mounted in the fluid system.
An objective of the present invention has been to provide a very simple and inexpensive blood pressure monitor.
Monitoring of temperature presents different problems. The mouth or rectal thermometer is of course well known. It is not useful for providing continuous real time monitoring.
A thermocouple has been used. The problem with the thermocouple is that it is difficult to maintain an electrical isolation of the patient, and there is, therefore, the possibility of heart fibrilation arising out of the use of the thermocouple.